The invention relates to a weft yarn changer on a projectile loom and to a projectile loom having such a weft yarn changer.
By means of a yarn transfer element forming part of the weft yarn changer and conventionally known as a yarn giver or retractor the tip of the weft yarn near the cutters is moved in front of the shed after picking and, by means of a yarn tensioner, drawn back and by means of the same yarn transfer element or in the event of a yarn change by means of some other yarn transfer element the yarn for the next pick is transferred to the projectile by means of gripper openers. The changer member has guideways or slideways for the yarn transfer elements. When the same are in their withdrawn position a required color or weft yarn change can be made by pivoting the changer member through one or more steps.
In the course of projectile loom development, which led to over-increasing productivity inter alia because of increasing loom speeds, no outstanding improvements were needed for a long time to the weft yarn changers of multicolor looms (cf. DE-PS 942979 ). In the end, however, the weft yarn changer turned out to be a speed-determining element. It became necessary, more particularly in the case of fabrics having e.g. four weft colors, where the color sequence called for maximum pivoting movements of the changer, to reduce loom speed considerably below that of two-color or mixing changer looms. This led to the patterns of some fabrics being so modified that color changing involving extreme changing steps was avoided with a view to greatly reducing changer strokes and thus enabling loom operating speeds to be higher. The resulting limitation of color selection meant of course that the problem was not solved satisfactorily. The solution of the problem had to be looked for in an improvement of the loom.